My research interests are the transcriptional regulation of tissue-specific gene expression and the mechanism of commitment of a cell to a particular differentiation pathway. The induction of neuronal differentiation in PC12 cells by nerve growth factor (NGF) is a model system for studying these questions. In order to understand the mechanism by which NGF triggers neuronal differentiation, we are studying the regulation of the peripherin gene, a neural-specific intermediate filament protein which is transcriptionally induced at the time of neuronal differentiation. Previously we have defined proximal; and distal positive elements in the peripherin promoter which are necessary for induction by NGF, as well as a negative regulatory element (NRE) which has a functional role in repressing peripherin activity in undifferentiated and non-neuronal cells. Our present focus is to identify positive and negative transcription factors which interact with these regulatory regions. This proposal will focus on the negative regulation of peripherin by repressor proteins binding to the NRE. A major goal is to purify and clone the repressor protein in order to determine how NGF-mediated mechanisms modify its expression and activity. In addition, possession of the cloned repressor protein will facilitate studies using in vitro transcription to define its level of action, as well as structural studies identifying the repressor domain of the protein. Finally, the effect of mutation at the NRE on the expression pattern of a peripherin promoter-lacZ fusion gene in transgenic mice will indicate the in vivo importance of the NRE for neuronal-specific expression.